Symbolism, Imagery, Allegory
Custance has a nasty habit of being set adrift at sea. May we recommend a navigating class?
But Chaucer isn't just being repetitive here. As it turns out, the recurring rudderless boat in which Custance finds herself adrift on the ocean is a very meaningful symbol in medieval culture. St. Augustine wrote that Noah's ark (also, as it happens, rudderless) symbolized the Christian church, carrying its believers safely through the storms of life's adversity. The underside of the roofs of Medieval cathedrals resembled an upside-down ship. Readers of the "Man of Law's Tale" would probably have immediately made this connection between Custance's boat and the Christian church.
But what are we to make of the fact that the boat is rudderless? Well, one of the most important themes of the "Tale" is man's powerlessness at the hands of fate or God. The rudderless-ness of Custance's boat could symbolize how powerless we are over our final destination. When in her boat on the open ocean, Custance is helpless before God. The whole combination of boat-and-passenger could symbolize a Christian passively carried throughout life by the provenance of God and the safety of the Church.